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Translucent Rock

Posted by Garrett Moore  
Garrett Moore February 22, 2010 09:43PM
Hello to All,

While working for an importer of antique furniture from Argentina in the 1980's, I found this rock rattling around behind the drawer of a heavily carved and expensive desk.
Due to the rock's unusual translucent appearance, rather than toss it in the bin, I kept it.
Upon examining the rock, I noticed that it had many concave divots, and the overall shape of a stone axe head.
However, the rock's size, 2.5 in x 2.75 in, appearance, and feel when held in my hand has always led me to believe it was possibly a flint knapping tool.

The rock cannot be scratched with a stainless steel knifeblade, and it has a somewhat shinier appearance inside of the divots.
While much of the surface is covered with small bubble-like inclusions which give it a frosty appearance, there are some spots where there are no "bubbles" which appear as a more solid underlying color.

When backlit, some areas appear nearly transparent, before becoming translucent.
When wetted, the rock goes a bit darker, and the bubble-like inclusions become more apparent.

Years ago, I stopped-in to a local rock shop and the man told me it was rose quartz, however I have never seen an example of rose quartz which looked like this rock does.
After an exhaustive search of the photos here at Mindat, I have not seen anything which looks like this rock.

Some additional high-rez photos at Webshots.

Thanks ahead of time for any comments, and thanks for an awesome website!

open | download - rock_01.JPG (638.2 KB)
open | download - rock_02.JPG (856.9 KB)
open | download - rock_03.JPG (811.3 KB)
Cobalt February 22, 2010 10:16PM
Agate definately
Cobalt February 22, 2010 10:50PM
dos not look like a napper tool unless you know any more info on it an the redness iron oxide. You could have someone cut an polish it for you?
Matt Neuzil February 22, 2010 10:53PM
could be a stained quartz pebble?

A buena hambre no hay pan duro
Anonymous User February 23, 2010 12:29AM
This is definately some variety of quartz. Not rose quartz, but most likely carnelian or as colbalt said, an agate. But deep orange internally solid quartz is reffered to as carnelian by most gem collectors. I have many peices of carnelian that look near identical to your secimen. Here in North Carolina I see specs of this size going from 30-50 dollars, but if I were you I would keep it as a sentimental memento. Hope the info helps.
Spencer Ivan Mather February 23, 2010 01:49PM
It looks like either carnelian or sard, whichever it is they are both examples of chalcedony? I have seen many like it on sale from Argentina!

Don Saathoff February 23, 2010 07:53PM
I'd call it chalcedony, variety carnelian......banding would move it to agate
Garrett Moore February 23, 2010 11:00PM
Thank you all for your learned comments.

I have had this rock for about 25 years, so it is very interesting to finally get some input as to what it actually is.
Haha...I have lost the rock twice, and at one point I asked my sister to put it in her aquarium so I would always know where to find it.
Ten years later I recently found my sister had placed it among some rocks my mother had collected on outings with a geology class she had taken after retiring.

OK,...there is no Quartz, va. Chalcedony, va. Carnelian?

Any explanations what caused the white inclusions?
Also, any ideas on these two spots which seem totally out of place for the rest of the surface?
The longer one on the right, seems to have a darker material inside it.
Thanks again one and all for your comments
Cobalt February 23, 2010 11:25PM
I think it's banding and does it need to have banding to be called agate?? Could there be a large growth of mineral to where there would be no banding?
Don Saathoff February 24, 2010 12:18AM definition a banded chalcedony is called agate and there many names for agate depending on the banding, inclusions, etc......BUT, the many colors & forms in which quartz occurs has led, down through thousands of years, to MANY names.....and some sellers are STILL creating new names to make their product more profitable and desireable.

Garrett....chalcedony often forms in bubbles in a volcanic in a rhyolite flow....any imperfections or patterns on the inside wall of the amygdule (ex-bubble) would transfer to the silica filling.
Jorge Dascal March 01, 2010 11:45AM
It is a chalcedony. There are few locations in Argentina, being the best I saw (deep red-orange-yellow) found in very few Patagonia remote areas on a rhyolite.

Jorge Dascal
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